Macromolecules Lab Report
Abstract The aim of the experiment is to test the existence of macromolecules which are carbohydrates, lipids, nucleic acids and proteins in given samples. The first experiment is to test the existence of carbohydrates in starch suspension and potato cell. If carbohydrate is present in starch suspension, the solution will turn into dark blue when iodine solution is added. If carbohydrate is present in potato cell, starch granules can be seen clearly under microscope when iodine solution is added. The second experiment is to test the existence of lipids in margarine and olive oil. If a lipid is present in margarine, the solution suspended with alcohol will turn cloudy when it is mixed with distilled water. If a lipid is present in olive oil, the solution suspended with alcohol will become cloudier than the margarine ones when it is mixed with water.
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The third experiment is to test the existence of nucleic acids in the epidermis of an onion.
If nucleic acid is present in the epidermis of the onion, the red-spot nucleus can be seen clearly when it is stained with aceto-orcein solution. The last experiment is to test the existence of proteins in cooked egg white. If protein is present in cooked egg white, the transparent solution of sodium hydroxide and cooked egg white will turn into purple when it is mixed with copper sulfate solution. Therefore, all macromolecules exist in all given samples. Introduction Macromolecules are large organic molecules which can be categorized into four major classes. They are carbohydrates, lipids, nucleic acids and proteins. Carbohydrates are the most abundant of these four macromolecules. Its basic units are called monosaccharide such as glucose, galactose and fructose. Monosaccharide can be linked together to form disaccharide and polysaccharide such as starch and cellulose. There are many functions of carbohydrates such as storage and transport of energy (starch) and structural component
(cellulose). Lipids are defined as any fat-soluble, naturally-occurring molecule such as fats, oils, waxes and steroids. Its basic units are triglycerides which consist of a glycerol and three fatty acids molecules. There are two types of lipids; saturated lipids (fat) and unsaturated lipids (oil). The main biological functions of lipids include energy storage, acting as structural components of cell membranes, and participating as important signaling molecules. Nucleic acids are made up of subunits called nucleotides which are joined together in long chains. Each nucleotide consists of a nitrogenous base, pentose sugar and phosphate group. There are two types of nucleic acids which are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main role of DNA molecules is the long-term storage of information while RNA serves as an essential carrier molecule for amino acids to be used in protein synthesis. Proteins are large molecules made up of different amino acids which are joined together by peptide bonds. There are four structure types of proteins; primary structure, secondary structure, tertiary structure and quaternary structure. Proteins are very important in cells as it acts as enzymes, structural proteins and cell signaling. Material Starch suspension, iodine solution, potato, margarine, alcohol, distilled water, olive oil, onion, aceto-orcein, cooked egg-white, sodium hydroxide solution, copper sulfate solution, light microscope, test tube with stopper, scalpel, microscope slide with cover slip, measuring cylinder, hot plate, water bath. Method Test for carbohydrate (starch) {text:list-item} {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for lipids {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for nucleic acids {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for proteins {text:list-item} {text:list-item} After the mixture is cooled, 5 ml of copper sulfate solution is added. The mixture is allowed to stand for several minutes and the colour change is recorded. Results A Test for carbohydrate (starch) In the first test, the colour of starch suspension when added with iodine solution changes into dark blue. The second test also shows positive result as starch granules can be seen clearly under microscope when iodine is added into the specimen. {draw:rect} B Test for lipids {draw:rect} In the second experiment, the mixture of suspended lipids in alcohol will turn cloudy when it reacts with water. Result shows that unsaturated olive oil is cloudier than saturated margarine when tested. C Test for nucleic acid In the third experiment, the stained nucleus of epidermis cell with aceto-orcein solution can be clearly seen as a red spot under light microscope. {draw:rect} D Test for proteins In the test for protein, the cooked egg white turns into yellowish jelly-like substance after warming it with sodium hydroxide. When copper sulfate is added, the colour of the mixture will change into purple. Discussion In the first test, iodine changes its colour from yellow to dark blue when dropped into the starch solution. It is because starch forms a complex polyiodide with iodine, which causes the blue-black solution to fore. Iodine is not very soluble in water; therefore it is dissolved in water with the presence of potassium iodide. This leads to the formation of linear triiodide ion complex which is soluble in water. I2+ I- '' I3- Natural starches can be separated into two fractions ' amylopectin and amylase. Triiodide ion, I3-, can slips into the coils of amylase, and reacts with the starch molecules. As a result, polyiodide complex formed, which is responsible for the dark blue colour. When water is added in the mixture of lipid and alcohol, a cloudy white suspension formed. This can be explained in terms of the polarity of the lipid molecules. Lipid is a non polar substance which does not dissolve in water. However, lipid can be dissolved in organic solvent such as alcohol. When this mixture reacts with water, the emulsion of lipids formed. It reflects the light and gives a white opalescent appearance. The alcohol acts as emulsifier, as it has polar and non-polar parts which can interact with both water and lipids. It breaks the lipid into smaller fragment which cause them to suspend in water. In comparison, olive oil has a higher proportion of unsaturated fat compared to hydrogenated margarine. As olive oil is in lipid form, it spreads easily in the alcohol when shaken rather than clump together like margarine. Therefore more suspended droplets form when it is mixed with water. This is why olive oil appeared to be cloudier than margarine when tested. The third experiment uses aceto-orcein to stain the nucleus in the epidermis cell. When the slide with the aceto-orcein is observed under microscope, the nucleus can be clearly seen as a red spot. This is because the aceto-orcein stains the nucleic acids of the nuclei thus make the nucleus visible, compared to the slide which is not stained with aceto-orcein. For the test of proteins, the copper sulfate changes colour from blue to violet when dropped into the cooled egg white solution. The copper atom reacts with the peptide bond of the egg-white protein, thus produce the colour change. Sodium hydroxide which added earlier before warming provides the alkaline condition, which is necessary in this reaction. Conclusion Hypothesis is valid. The results show positive effects for all experiments, indicating the existence of macromolecules in all given samples.
The third experiment is to test the existence of nucleic acids in the epidermis of an onion.
If nucleic acid is present in the epidermis of the onion, the red-spot nucleus can be seen clearly when it is stained with aceto-orcein solution. The last experiment is to test the existence of proteins in cooked egg white. If protein is present in cooked egg white, the transparent solution of sodium hydroxide and cooked egg white will turn into purple when it is mixed with copper sulfate solution. Therefore, all macromolecules exist in all given samples. Introduction Macromolecules are large organic molecules which can be categorized into four major classes. They are carbohydrates, lipids, nucleic acids and proteins. Carbohydrates are the most abundant of these four macromolecules. Its basic units are called monosaccharide such as glucose, galactose and fructose. Monosaccharide can be linked together to form disaccharide and polysaccharide such as starch and cellulose. There are many functions of carbohydrates such as storage and transport of energy (starch) and structural component
(cellulose). Lipids are defined as any fat-soluble, naturally-occurring molecule such as fats, oils, waxes and steroids. Its basic units are triglycerides which consist of a glycerol and three fatty acids molecules. There are two types of lipids; saturated lipids (fat) and unsaturated lipids (oil). The main biological functions of lipids include energy storage, acting as structural components of cell membranes, and participating as important signaling molecules. Nucleic acids are made up of subunits called nucleotides which are joined together in long chains. Each nucleotide consists of a nitrogenous base, pentose sugar and phosphate group. There are two types of nucleic acids which are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main role of DNA molecules is the long-term storage of information while RNA serves as an essential carrier molecule for amino acids to be used in protein synthesis. Proteins are large molecules made up of different amino acids which are joined together by peptide bonds. There are four structure types of proteins; primary structure, secondary structure, tertiary structure and quaternary structure. Proteins are very important in cells as it acts as enzymes, structural proteins and cell signaling. Material Starch suspension, iodine solution, potato, margarine, alcohol, distilled water, olive oil, onion, aceto-orcein, cooked egg-white, sodium hydroxide solution, copper sulfate solution, light microscope, test tube with stopper, scalpel, microscope slide with cover slip, measuring cylinder, hot plate, water bath. Method Test for carbohydrate (starch) {text:list-item} {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for lipids {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for nucleic acids {text:list-item} {text:list-item} {text:list-item} {text:list-item} Test for proteins {text:list-item} {text:list-item} After the mixture is cooled, 5 ml of copper sulfate solution is added. The mixture is allowed to stand for several minutes and the colour change is recorded. Results A Test for carbohydrate (starch) In the first test, the colour of starch suspension when added with iodine solution changes into dark blue. The second test also shows positive result as starch granules can be seen clearly under microscope when iodine is added into the specimen. {draw:rect} B Test for lipids {draw:rect} In the second experiment, the mixture of suspended lipids in alcohol will turn cloudy when it reacts with water. Result shows that unsaturated olive oil is cloudier than saturated margarine when tested. C Test for nucleic acid In the third experiment, the stained nucleus of epidermis cell with aceto-orcein solution can be clearly seen as a red spot under light microscope. {draw:rect} D Test for proteins In the test for protein, the cooked egg white turns into yellowish jelly-like substance after warming it with sodium hydroxide. When copper sulfate is added, the colour of the mixture will change into purple. Discussion In the first test, iodine changes its colour from yellow to dark blue when dropped into the starch solution. It is because starch forms a complex polyiodide with iodine, which causes the blue-black solution to fore. Iodine is not very soluble in water; therefore it is dissolved in water with the presence of potassium iodide. This leads to the formation of linear triiodide ion complex which is soluble in water. I2+ I- '' I3- Natural starches can be separated into two fractions ' amylopectin and amylase. Triiodide ion, I3-, can slips into the coils of amylase, and reacts with the starch molecules. As a result, polyiodide complex formed, which is responsible for the dark blue colour. When water is added in the mixture of lipid and alcohol, a cloudy white suspension formed. This can be explained in terms of the polarity of the lipid molecules. Lipid is a non polar substance which does not dissolve in water. However, lipid can be dissolved in organic solvent such as alcohol. When this mixture reacts with water, the emulsion of lipids formed. It reflects the light and gives a white opalescent appearance. The alcohol acts as emulsifier, as it has polar and non-polar parts which can interact with both water and lipids. It breaks the lipid into smaller fragment which cause them to suspend in water. In comparison, olive oil has a higher proportion of unsaturated fat compared to hydrogenated margarine. As olive oil is in lipid form, it spreads easily in the alcohol when shaken rather than clump together like margarine. Therefore more suspended droplets form when it is mixed with water. This is why olive oil appeared to be cloudier than margarine when tested. The third experiment uses aceto-orcein to stain the nucleus in the epidermis cell. When the slide with the aceto-orcein is observed under microscope, the nucleus can be clearly seen as a red spot. This is because the aceto-orcein stains the nucleic acids of the nuclei thus make the nucleus visible, compared to the slide which is not stained with aceto-orcein. For the test of proteins, the copper sulfate changes colour from blue to violet when dropped into the cooled egg white solution. The copper atom reacts with the peptide bond of the egg-white protein, thus produce the colour change. Sodium hydroxide which added earlier before warming provides the alkaline condition, which is necessary in this reaction. Conclusion Hypothesis is valid. The results show positive effects for all experiments, indicating the existence of macromolecules in all given samples.